The present invention relates to a laser system for irrigation, including debriding, cleaning and decontamination, of anatomical cavities filled with a liquid.
There are many medical treatments, such as in endodontics, periodontics, implantology, or bone surgery where an effective irrigation, including debriding, cleaning and decontamination of the anatomical cavities is desirable.
For example, a goal of endodontic treatment is typically to obtain an effective cleaning and decontamination of the root canal system (e.g., removal of bacteria and other contaminants from the smear layer). Clinically, traditional endodontic techniques use mechanical instruments as well as ultrasound and chemical irrigation, in an attempt to shape, clean and completely decontaminate the endodontic system.
The complexity of the root canal system is well known. Numerous lateral canals (with various dimensions and with multiple morphologies) branch off from the principal canals. The effectiveness of debriding, cleaning and decontaminating effectively all the intra-radicular space is often limited, given the anatomical complexity and given the inability of common irrigants to penetrate into the lateral canals and/or the apical ramifications. A debriding, cleaning and decontaminating effectively of the root system thus represents a challenge.
Similarly, when creating a hole in hard body tissue like bone material, using the mechanical tools such as drill or saw, tissue particles debris is left on the tissue surface leading to a smear layer on the treated surface. This may lead to increased inflammatory response and decelerated tissue regeneration and attachment. This is for example important in implantology where faster attachment of the bone to the inserted implants is crucial for faster patient recovery time. A minimally invasive improved means for the cleaning, debriding and disinfection of the holes created during bone surgery are therefore desirable. Also, in order to stop inflammations that occur after the surgery, and to promote re-attachment, an improved means for the cleaning, debriding and disinfection of the surfaces of the already inserted implants and the surrounding bone surfaces are also desirable.
Use of lasers has been studied in endodontics since the early 1970s, and lasers are now widely used in dental applications. Early attempts at laser use in endodontics typically resulted in occlusion of dentinal tubules, thereby undesirably decreasing their permeability. Some early reports indicated a reduction of bacterial load, although in connection with unwanted generation of heat. More recent investigations have focused on laser-activated irrigation approaches that produce explosive vapor bubbles with acoustic transients effects, facilitating removal of debris from intricate tooth anatomy. These approaches permit fluid interchange and the removal of organic tissue and microbes, resulting in tubular dentin disinfection.
In a prior laser irrigation method (for example, as disclosed in U.S. Pat. No. 7,980,854), a laser system contains a source of a laser light beam. An elongate optical fiber is connected to the laser source and is configured to transmit the laser light beam to a tip. The tip is substantially completely immersed into a liquid introduced into the open area of a pulp chamber to provide a liquid reservoir. In this prior laser irrigation method, the laser source is pulsed at a power level from about 0.1 watts to about 1.5 watts, at a pulse duration from about 100 nanoseconds to about 1000 microseconds, at a pulse frequency from about 2 Hertz (Hz) to about 25 Hz, and over a cycle time of from about 10 seconds to about 40 seconds. In this prior system, solid state lasers having a wavelength of from about 700 nanometers (nm) to about 3000 nm are contemplated, such as Nd:YAG (neodymium-doped yttrium aluminum garnet), Er:YAG (erbium-doped yttrium aluminum garnet), Ho:YAG (holmium-doped yttrium aluminum garnet), Nd:YLF (neodymium-doped yttrium lithium fluoride), titanium sapphire, or Er,Cr:YSSG (erbium, chromium doped yttrium scandium gallium garnet) lasers. The interaction of the pulsed laser beam with the liquid is contemplated to result in a rinsing, irrigating and disinfecting of the pulp chamber and root canal to provide substantially clean and pulp-free dentin walls lining the chamber and root canal ready for subsequent filling.
In this prior method, laser pulses are delivered into the liquid at a relatively slow repetition rate of 2 to 25 Hz. There is therefore no substantial interaction between the acoustic transients caused by individual pulses, resulting in a limited laser light-to-acoustic (LA) energy conversion efficiency. Even more importantly, in this prior art method, the bacteria within the treated anatomical cavity are submitted to acoustic transients of a relatively short duration. It is well known, however, that when bacteria are submitted to increased temperatures, the kill rate depends not only on the amplitude of the temperature increase, but even more importantly, on the temporal duration of the temperature increase, the exact dependence being described by the standard Arrhenius integral. Similar consideration applies also when bacteria are submitted to acoustic transients. When subjected to acoustic transients, the bacteria's structure is disrupted and the bacteria die, providing that the exposure to the transients is extensive enough to be fatal. Bacteria kill rate will be much higher when bacteria are submitted to acoustic transients for a longer duration of time, preferably longer than 1000 μs. Accordingly, even after disclosure of prior laser irrigation methods, it remains desirable to provide improved laser irrigation devices and/or methods wherein the laser treatment parameters are adjusted and/or optimized to obtain stronger and longer lasting acoustic transients.
Moreover, the prior art method requires that the laser energy is delivered into the liquid reservoir within the pulp chamber and root canal in a “contact” manner, by means of an elongate optical fiber configured to transmit laser light beam from a laser source to a conical fiber tip which is substantially immersed into the liquid reservoir, and the light beam is emitted from the tip generally omnidirectionally. There are at least two shortcomings of this approach: i) Special tip is required to perform the treatment, which adds to the complexity and cost of the treatment. Moreover, the fiber tip is susceptible to damage since it can get at least partially shattered under the strong acoustic transients within the liquid. Undesirable fragmented fiber particles may therefore remain within the cavity after the treatment. This makes the prior art method less safe, and also less effective since the strength of the acoustic transients must be adjusted to be below the damage threshold of the fiber tip; ii) The angular distribution of a laser beam coming out of an elongate fiber is broad and omnidirectional with a lack of collimation, which results in insufficient laser energy conversion.
Accordingly, improved methods, techniques and technologies that can improve irrigation, including cleaning, debriding and disinfection of anatomical cavities (e.g., root canal systems, periodontal pockets, surgical holes and the like) are desirable. In particular, even after disclosure of prior laser irrigation methods, it remains desirable to provide improved, less invasive laser irrigation devices and/or methods wherein the laser treatment parameters are adjusted and/or optimized to obtain stronger and longer lasting acoustic transients without the need to increase the single pulse energy or the cumulative energy delivered to a liquid during a treatment.
The object of the present invention is to provide an improved laser system with a better laser energy conversion for improved irrigation results.